1. Field of the Invention
The present invention relates to a vehicle driving-force control device having a manual shift mode in controlling an automatic shift in which one of a plurality of preset gear stages can be manually selected.
2. Description of the Related Art
For a power train to be mounted on a vehicle, there have been many technologies are disclosed that provide a plurality of modes that generate different driving force characteristics in response to a driver's accelerator operation so that a running performance which values high fuel efficiency, a sporty driving or the like is achieved.
For example, Japanese Patent Publication No. 3872507 discloses a technology that sets, as driving force characteristics, a normal mode in which output torque substantially linearly changes with respect to an accelerator opening degree, a save mode in which engine torque is saved to achieve both ease of driving and fuel efficiency, and a power mode in which a particular value is placed on power and an excellent output characteristic in response is achieved across from a low engine speed range to a high engine speed range. Any one of these driving modes can be selected according to a driver's preference in response to an input operation from a shuttle switch disposed on a center console.
A continuously variable transmission is well known as an automatic transmission that constitutes a power train of this type. The continuously variable transmission has shifts modes including an automatic shift mode for automatically controlling a gear ratio according to a preset transmission characteristic as well as a manual shift mode for manually selecting one of a plurality of preset gear stages so as to shift to a specifically fixed gear ratio. In this case, the gear ratio is basically kept on a fixed gear ratio of a gear stage selected by a driver in the manual shift mode. In a case, for example, where an input speed of the continuously variable transmission exceeds a preset and fixed speed for automatic upshift/downshift, the gear stage is forced to be shifted up/down from a viewpoint of engine protection or the like.
In a driving force control device having the automatic transmission described above, however, the gear stage selected by the driver is maintained in a preset speed range for automatic upshifting/downshifting in the manual shift mode having been selected.
Thus, in the above-mentioned speed range, preset downshift is not performed even if the driver presses an accelerator pedal deeply and a kick-down switch is turned on. Accordingly, a shift operation is performed against the driver's intention.